The present invention relates to an ink jet recording head and a manufacturing method thereof. More to particularly, this invention relates to an ink jet recording head and a manufacturing method thereof, in which it is capable of being arranged multi-nozzle and high density nozzle, being in use for a printer, facsimile, or copying machine.
Formerly, this kind of the ink jet recording device is capable of being divided into largely two classes in terms of the point of ink discharge drive source.
One is a method so called as thermal ink jet or bubble jet, for instance, being disclosed in the Japanese Patent Publication No. SHO 61-59913. This method is a method in which pressure chambers are formed in answer to respective thermal elements on a thermal head to which a plurality of thermal elements are arranged, and a nozzle and an ink supply path open to the pressure chamber, at the time of printing, causing the thermal element to be energized to heat an ink to generate a bubble, so that it causes the ink to be discharged from the nozzle by virtue of the pressure of the bubble.
With respect to this type, a thermal head which is a discharge source is capable of being manufactured by photo-lithography technology so that there can be formed a printing head with high density and with a multi-nozzle, thus enabling small-sized and high-speed ink jet recording device to be obtained. However, it is necessary to heat ink more than 300xe2x96xa1. in order to generate a bubble. For that reason, when discharge is implemented for a long time, ingredients within the ink are accumulated on the thermal element to cause inferior discharge; further, there occurs damage caused by thermal stress or cavitation, and passivation trouble caused by pinhole of a protective layer of the thermal element. Thus it is difficult to obtain a long life printing head.
The other method is a so called piezoelectric method, for instance, being disclosed in the Japanese Patent Publication No. SHO 53-12138. The piezoelectric method consists of a pressure chamber together opening into both of a nozzle and an ink supply path, and a piezoelectric element generating volume change to the pressure chamber. At the time of printing, there is applied voltage to the piezoelectric element in order to generate the volume change to the pressure chamber to discharge ink from the nozzle.
With respect to the piezoelectric method, since the ink is not heated, the degree of freedom of ink selection is high, and has a long life; however, it is difficult to arrange many piezoelectric elements in a high density, and it is difficult to obtain small-sized and high speed ink jet recording device.
For that reason, in order to overcome such problems there is disclosed the matter shown in FIG. 1 in terms of the Japanese Patent Application Laid-Open No. HEI 6-143564. There is alternately formed ink channels 41bc, 41de, . . . , and dummy channels 42ab, 42ad, . . . , whose upper side covered with a top plate 44, and whose sides thereof surrounded by partition walls 43b, 43a, 43d, 43e, . . . , on a substrate 40 made of the piezoelectric element formed into one piece of a plate made of piezoelectric material. The ink is filled into only 41bc, 41de, . . . 
Furthermore, the partitions 43b, 43a, 43d, 43e, . . . polarize the partitions 43b, 43a, 43d, 43e, . . . as an arrow (polarization direction 47) using electrodes 48ba, 48cd, 48de, formed in the channel. In this case, the direction of the polarization is directed opposite each other at the adjacent partitions therebetween. When there is fixed the dummy channel out of the dummy channels 42ab, 42ad, . . . into common ground electric potential, and there is applied drive electric pulse to the ink channel, the partition elongates in the direction of the electric field so that it causes a volume within the ink channel to be changed to enable ink to be discharged.
In the above-described conventional ink jet recording head, when there is a defect in the protective layer protecting the electrode or there is an electrical withstand voltage failure with no defect, there is a problem that an electric field generated between individual electrode-common electrode interacts with the ink. The ink used generally, has certain electric conductivity, when the electric field interacts with the ink, there occurs electrolysis so that hydrogen is generated from the cathode, and oxygen is generated from anode. The generation of the hydrogen and the oxygen depends on the ink electric conductivity, the protective layer electrical characteristic, and the oxidation and reduction electric potential of the electrode material. In all cases, gasses occurrence produce bubbles within the ink channel to cause ink discharge failure. The gasses occurrence produces electrolysis so that the physical property value of the ink changes greatly. This matter greatly influences ink discharge characteristic.
Moreover, when the electrolysis reaction is large, the viscosity of the ink increases greatly, and there may occur blocking fluidity of the ink within the ink channel.
In view of the foregoing, it is an object of the present invention, in order to achieve the above mentioned problems, there is provided an ink jet recording head and a manufacturing method thereof in which there is prevented the occurrence of ink electrolysis caused by the individual configuration of the ink jet recording head using a piezoelectric body and mechanism.
According to a first aspect of the present invention, in order to achieve the above-mentioned object, there is provided an ink jet recording head in which an ink channel and a dummy channel are formed alternately in such a way that a side wall of a piezoelectric body intervenes between the ink channel and the dummy channel. Thus there is discharged an ink drop while changing the volume within the ink channel by applying an electric field to a channel using an electrode formed within respective channels, wherein an electrode formed on respective the ink channels is taken as a common electrode, while an electrode formed on respective the dummy channels is taken as an individual electrode, thus causing no ink to be contacted with a passivation film formed on the individual electrode.
According to a second aspect of the present invention there is provided an ink jet recording head which comprises a plate consisting of a piezoelectric body, a groove formed on the plate, a channel in which there exists an electrode on the inside of the groove, and whose both sides are partitioned by a side wall of the piezoelectric body, and whose upper side is covered by a top plate, a nozzle opening into the channel; and a control system. The control system includes a voltage apply means for applying an electric field to the electrode, in which the side wall intervenes adjacent ink channels therebetween so as to be held in common by the adjacent ink channels. There is taken alternate channel filled with an ink as an ink channel and another channel as dummy channel, thus causing ink drops to be discharged from the nozzle while deforming the wall of both sides constituting the ink channel. There is also taken an electrode formed on the ink channel as a common electrode, while it causes no ink to be contacted with a passivation film on an individual electrode formed on the dummy channel.
According to a third aspect of the present invention, there is provided a manufacturing method of the ink jet recording head which comprises the steps of forming a groove for functioning as an ink channel and a dummy channel on a piezoelectric body, forming an electrode layer on the inside of the groove, forming a passivation film on said electrode layer, uniting a nozzle plate and a top plate after forming the passivation film, and forming a slit at the top plate, wherein when there is formed the slit at the top plate, there is formed individual electrode by separating the electrode layer while implementing groove formation to the bottom surface of the dummy channel.
The above and further objects and novel features of the invention will be more fully understood from the following detailed description when the same is read in connection with the accompanying drawings. It should be expressly understood, however, that the drawings are for purpose of illustration only and are not intended as a definition of the limits of the invention.